Desmodromic variable valve actuation

ABSTRACT

The combination of the Fully Variable Valve Actuation or FVVA system with the Desmodromic control results in a fully functional FVVA rid of valve springs and any other kind of the restoring springs of the art.

The closest prior art is the U.S. patent application 11759392, of Jun. 07, 2007.

In a Fully Variable Valve Actuation, or FVVA, and in a Variable Valve Actuation, or VVA, system, the valve lift or the valve duration or both can vary to approach the desirable valve lift profile.

A Desmodromic valve train, as its name implies, holds the valve during the opening process and also during the closing process, eliminating the need for restoring valve springs.

This invention combines the FVVA/VVA with the Desmodromic mechanism to provide a valve train rid of restoring springs, fully functional, lighter, shorter, capable for higher revs, cheaper, with lower friction etc.

FIG. 1 shows a desmodromic fully variable valve actuation mechanism,

FIG. 2 shows a Lost Motion desmodromic variable valve actuation mechanism,

FIG. 3 shows, from two different points of view, a desmodromic fully variable valve actuation mechanism while

FIGS. 4 to 11 show the same mechanism after a step by step removal of various parts in order to reveal the inner parts,

FIG. 12 shows another embodiment of a desmodromic fully variable valve actuation mechanism.

The mechanism shown in FIG. 1 derives from the mechanism shown in the middle of FIG. 21 of U.S. 11759392 application.

In FIG. 1, the first control shaft 4 comprises two control surfaces 51 and 52.

The roller (31, 32) is actuated by a rotating eccentric pin 158 through a connecting rod 155. The ring 32 rolls along the control surface 52 and the pin 31 rolls along the control surface 51. The control surfaces 51 and 52 on the first control shaft 4, allow the motion of the center 153 of the roller (31, 32) only along the path 53 shown by dust dot line. The roller (31, 32) moves in substantially simultaneous abutment to both surfaces 51 and 52. Along a part of the path 53, the valve remains closed. It is the lost motion part.

The valve 11 is properly secured to the actuator 10.

A washer 114 is between the valve 11 and the bottom side of the actuator 10. A flexible washer 113 is at the upper side of the bottom of the actuator 10, and a nut 112 is fastened on the thread 111 of the valve stem, providing preloading adjustment, known from the art of desmodromic mechanisms.

Both control shafts can rotate about the axis at the cross 12. The second control shaft, not shown in FIG. 1, holds the center 156 of the lower pin of the rod 154 at a constant distance from the axis at the cross 12 and displaces it angularly to increase or decrease the valve lift. Rotating the first control shaft 4, the valve duration and the valve lift change but not independently: each valve lift is coupled to one and only valve duration and vice versa. Changing the angular displacement of both control shafts, the valve lift and the valve duration can vary independently.

In a four stroke engine, the eccentric pin can be secured on a shaft rotating with half the crankshaft speed. The same shaft with eccentric pins can serve all the intake valves of a cylinder head or even all the intake and all the exhaust valves of a cylinder head.

For applications where the simple Lost Motion VVA is adequate, the mechanism can be simplified as shows FIG. 2, omitting the two lower rods 9 and 154 and the second control shaft.

For friction reduction and minimization of the clearances, the roller mentioned above can comprise pins, rings, needles, balls etc known in the art.

The additional, beyond the conventional valve springs, massive restoring springs necessary in most state of the art VVA systems for the restoring of the parts of the VVA mechanism, and the difficulty of their installation is a major problem and many patents deal with it.

In the Desmodromic FVVA and VVA, there is no need of any restoring springs, neither for the valves nor for the parts of the VVA mechanism. The valves and the VVA parts move and restore to their rest position desmodromically.

In FIG. 1 the eccentric pin 158 rotates about the axis 157. The connecting rod 155 transfers the motion of the pin 158 to the roller (31, 32). The roller is forced to move along a path formed in the control shaft 4 by the control surfaces 51 and 52. The rod 152 is rotatably connected to the rod 155 at the axis 153. The rods 154 and 9 are rotatably connected to the rod 152 at the axis 151. The pin 156 of the rod 154 is angularly displaceable, about the axis at the cross 12, by the second control shaft. The lower end of the rod 9 is rotatably connected, at the axis 150, to the valve actuator 10. The valve actuator 10 holds the valve 11. As shown in the detail at the right of FIG. 1, the cylindrical member 10 can slide along a hole/bearing/guide 101. The valve 11 ends at a thread 111. A washer/height adjuster 114 is located between the valve 11 and the lower part of the bottom of the valve actuator 10. A flexible washer 113 is located on the upper side of the bottom of the valve actuator 10. The nut 112, fastened on the thread 111 of the valve 11, preloads the flexible washer 113. The flexible washer compensates for the thermal expansion and keeps the valve in secure contact to the valve seat when the valve is at rest. The 114 washer can also be flexible.

FIG. 3 shows the mechanism of FIG. 1 applied on a pair of valves. Both control shafts are shown. In FIG. 4 the first control shaft 4 is removed. In FIG. 5 the second control shaft is also removed. In FIG. 6 the shaft with the eccentric pins is removed.

In FIG. 7 the roller (31, 32) is removed. In FIG. 8 the connecting rods 155 are removed. In FIG. 9 the rods 152 are removed. FIG. 10 shows only the valves and the actuators. FIG. 11 shows in detail the connection of the valve 11 to the valve actuator 10.

Locking the first control shaft at an angle, the system of FIG. 1 to 11 becomes a Constant Duration Desmodromic VVA.

FIG. 12 shows a different embodiment of the desmodromic VVA mechanism. The eccentric pin 158 displaces, via the connecting rod 155, the upper end of the rod 154. The lower end of the rod 154 is displaceable about the axis at the cross 122 by a control shaft similar to the second control shaft mentioned in the first embodiment. The rod 152, rotatably connected to the rods 155 and 154, displaces the roller (31, 32). The roller (31, 32) is in substantially simultaneous abutment to the two control surfaces 51 and 52 of the control shaft 4. The control shaft 4 is rotatable about the axis at the cross 121. The roller (31, 32) displaces the valve actuator 10 and the valve 11, via the rod 9. The system is a FVVA and at the same time a desmodromic valve train, capable to operate without valve spring and without any other restoring springs for the parts of the VVA mechanism.

In the previous, the actuation of the VVA mechanism by a rotating eccentric pin, through a connecting rod, was the case. Several alternatives of the reciprocating pin, known from the art, can be used instead, like the mechanism of the PCT/GR04/000052 application that provides linear reciprocation or the harmonically reciprocating pin of the mechanism of the PCT/GR91/00004 application.

Although the invention has been described and illustrated in detail, the spirit and scope of the present invention are to be limited only by the terms of the appended claims. 

1. A desmodromic mechanical valve train system for the control of the motion of a valve of an engine, characterized in that the valve lift profile is variable according the state of at least one control member, thereby a desmodromic variable valve actuation system is provided.
 2. A mechanical variable valve actuation system for the control of a valve of an engine, characterized in that the valve motion is controlled desmodromically.
 3. As in claim 1 wherein a first control member and a second control member provide independently variable valve lift and valve duration.
 4. As in claim 2 wherein the variable valve actuation system is a fully variable valve actuation system providing independently variable valve lift and valve duration.
 5. As in claim 2 wherein an eccentric pin rotates or reciprocates or oscillates in synchronization with the engine, said eccentric pin, via a connecting rod, displaces a roller, said roller is in substantially simultaneous abutment to two control surfaces of a control member, said two control surfaces have form and location such that, in combination with the connecting rod action, force the roller to perform a desmodromic motion, said roller imparts, via another connecting rod, its motion to the valve.
 6. As in claim 2 wherein an eccentric pin rotates or reciprocates or oscillates in synchronization with the engine, said eccentric pin, via a connecting rod, displaces a roller, said roller is in substantially simultaneous abutment to two control surfaces of a control member, said two control surfaces have form and location such that, in combination with the connecting rod action, force the roller to perform a desmodromic motion, said two control surfaces include a lost motion part and an actuation part, said roller imparts, via another connecting rod, its motion to the valve.
 7. A mechanical constant duration variable valve actuation system for the control of the valve lift of a valve of an engine, characterized in that the valve motion is controlled desmodromically.
 8. As in claim 7 wherein an eccentric pin rotates or reciprocates or oscillates in synchronization with the engine, said eccentric pin, via a connecting rod, displaces a roller, said roller is in substantially simultaneous abutment to two, substantially immovable relative to the engine, surfaces, said two control surfaces have form and location such that, in combination with the connecting rod action, force the roller to perform a desmodromic motion, said two control surfaces include a lost motion part and an actuation part, said roller imparts, via another connecting rod, its motion to the valve.
 9. As in claim 2 wherein a reciprocating or rotating or oscillating pin, via a connecting rod, actuates desmodromically a constant duration mechanism which in turn actuates desmodromically a lost motion mechanism, which in turn actuates desmodromically the valve. 